How a Torsion Bar Works

by Editorial Team
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A torsion bar is a flexible spring that can be moved about its axis via twisting. Torsion bars are designed and based on the amount of torque used in the twisting of the spring, the angle of the twist, the overall dimensions of the torsion bar and what materials the torsion bar is made from.

The most common place to find a torsion bar is in the suspension of a car or truck, in machines used for production or in other precision devices. The flexibility of the spring is the main reason that a torsion bar is used. If a more rigid structure were used such as a steel rod were used too much load bearing pressure would be placed on the both the wheels and the under body of the vehicle.

How a Torsion Bar Works

A torsion bar works by resisting the torque placed on it. When one end of the torsion bar is affixed to an object that cannot be moved, the other end of the bar is twisted, thus causing torque to build up. When this happens, the torsion bar is resistant to the torque and will quickly go back to its starting position once the torque is removed. In general, the object that cannot be moved is usually a frame. If there is not any force applied to the torsion bar, it will stay at the same position until force is applied.

Practical Example

An example the other end of the bar will be contacted to a control arm. The control arm moves in a fixed manner on the frame and this creates the twisting movement on the bar. This, in turn, supplies the torque needed to make a spring.

Torsion Bar Adjustments

Occasionally, there may be a need to adjust the height of a vehicle. This is done by using the adjuster bolt located at the frame end of the torsion bar. The weight placed on the control arm of the torsion bar in unchanged when this adjustment is made. Once the torsion bar is manipulated in this manner, rides in the vehicle may feel somewhat stiffer. This is due to the new angle of the control arm. It is also a possibility that the adjuster bolts may have been wound too far. This causes a lack of room between the control arm of the vehicle and the upper portion of the torsion bar closest to the under side of the vehicle. After making a change to the height of the torsion bar, it is a good idea to have the alignment of your vehicle checked to make the sure the weight of the vehicle body is properly distributed.

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